@keyframes intro-loading {
  to {
    transform: rotate(360deg);
  }
}

.intro-loading {
  position: relative;
  color: transparent;
}

.intro-loading:before {
  content: '';
  box-sizing: border-box;
  position: absolute;
  top: 50%;
  left: 50%;
  width: 20px;
  height: 20px;
  margin-top: -10px;
  margin-left: -10px;
  border-radius: 50%;
  border: 2px solid #ccc;
  border-top-color: #000;
  animation: intro-loading .6s linear infinite;
}